Question 1134991
You start with 700, so  at m=0, s=700 (or s(0) = 700  in functional notation).<br>

After 1 month, you will have added $75, so  s(1) = 700+75 = 775
After 2 months, you will have added 2*$75 so s(2) = 700+2*75 = 850
...

After m months, you will have added m*$75 so s(m) = 700+m*75 or, writing 75m instead of 75*m:  {{{highlight( s(m) = 700+75m) }}}<br>

(This whole discussion assumes no interest is accumulating)<br>

To figure out how many months it would take to save $10000, set s(m) to 10000 and solve for m:  
 
{{{ highlight(700+75m = 10000) }}}

m = (10000 - 700)/75 = __________     you can do the arithmetic